Chinese miners last year dug up 3.87 billion tonnes of coal, more than enough to keep all four of the next largest users – the United States, India, the European Union and Russia – supplied for a year.

The country has grappled for years with the direct costs of that coal, in miners’ lives and the more widespread impact of crippling air pollution.

The less immediate costs of the main fuel for China’s decades-long boom are now also becoming ever clearer, in drying riverbeds, shrinking rainfall and expanding deserts.

In one northwestern province alone the government has moved nearly a quarter of a million “environmental refugees” from homes made uninhabitable by drought and rising temperatures.

Clean energy programmes and a slowing economy helped cut coal use last year for the first time in over a decade.

Desire for change contends though with universal fears about employment and slowing growth, and efforts to cut consumption do not always mean a clampdown on mining.

Chapter 1

Most of the mines burrowed into the parched hillsides of Wang Family Mountain have been closed for several years, but their shadow lingers in the blackened, failing lungs of the He family.

The mining carried He Jinbao off first, then two of his seven sons. Now two more He brothers are waiting to die, condemned by dust inhaled long ago on underground shifts.

The tiny airborne specks pose a risk few miners understand as they head down into the country’s pits, haunted by the more immediate fear of the explosions and collapses which claim hundreds of lives each year.

“I never heard anyone mention black lung disease,” said He Quanfa, one of the two doomed brothers – there is no cure for the illness which slowly hardens the lungs as they try to expel trapped coal dust. “If I had, I might have worn a mask.”

Already short of breath, he knows what little he can expect from the brief remains of his life because he watched the same disease ravage his father and brothers.

They all hung up their hard hats years before their diagnoses, and thought they had escaped the mines with not just their lives but also a tiny slice of the country’s new-found prosperity. “Until fifteen years ago, we lived in a cave,” says He, now 50.

Instead he was already nursing an incurable disease that has killed hundreds of thousands of Chinese workers, and may claim up to six million more in coming years, one charity that works with suffers <a href="http://www.daaiqingchen.org/list.php?fid=49" target="_blank">estimates</a>. Even conservative government data shows that each year the number of registered sufferers leaps by around a third.

For the seven sons of the He family, the mines were the only route out of absolute poverty in their dusty corner of the northwest, where there was little farmland and less water to irrigate it.

They all left school early, barely literate and all ended up in the mines.

The cash they earned hacking out coal covered their children’s school fees and built the brothers’ first brick homes – quiet courtyards filled with sunlight, the soft songs of nesting swallows, and now a bitter sense of regret.

“He paid for this house with his life,” said He Quanfa’s wife, waving listlessly at wooden beams, elegant calligraphy and a cabinet stuffed with medical papers and x-rays that chart the relentless decay of her husband’s lungs. Last year five of his friends from the mine slipped away.

He spent most of the winter watching TV in the kitchen, hooked up to an oxygen compressor and trying to stay warm and dry, terrified of catching a cold that could overwhelm his battered lungs.

He has not been able to work for years, so they survive on vegetables and melons grown by his wife and money sent home by two sons, riddled by guilt that the boys can’t save up for marriage.

A few dozen meters away his younger brother He Quanying is even more desperate.

His disease is less advanced but it has shattered the family more profoundly, because his wife was badly injured in a road accident around the time that his lungs began seizing up, and she can no longer work at all.

They only eat two meals a day to help scrape together school fees for their son from a social security payment of 300 yuan a month (about £35). He is studying for an engineering diploma that will take a third generation into mining, but at least keep him further away from the deadly dust.

Two years ago the Love Save Pneumoconiosis charity paid for a lavage, or rinse of He Quanying’s lungs, which eased the symptoms, but it cost more than the family scrapes together to live off in a year, so another is out of the question.

“Talking about it is a waste of time,” he says. “I have no place to go complain because I got this disease from earning a living. Fair or not, we did it.”

Even if he wanted to, there is no one to sue for compensation or petition for help with medical fees.

The private mine where he worked without contracts, insurance or protection shut around two years ago and the owner vanished soon after.

The mine was probably a target of belated government efforts to halt the accidents that kill hundreds of men a year, and professionalise a critical sector, by closing down the small independent pits whose business model is usually based on bribing their way out of regulations.